Positron Emission Tomography (PET), using 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) as the imaging probe, has been proven to be a valuable tool for the early detection, staging, and restaging of cancer. However, despite the clear value of PET imaging, limitations do exist, since current imaging probes may lack specificity or have inadequate signal to background characteristics in vivo. Additional biomarkers are needed that show a very high affinity to and specificity for tumor targets to support cancer drug development and to provide health care providers with better diagnostic tools. Such high-affinity imaging probes could dramatically improve the apparent spatial resolution of the PET scanner, allowing smaller tumors and lower concentration disease targets to be detected. We will address this need by creating a generalizable technology platform based on the fragment-based in situ click chemistry approach in combination with microfluidics technologies to identify high-affinity PET probes that target cancer-related proteins. For platform development and validation, we will employ the cancer-related kinase Akt. The UCLA/CalTech/MTI team is an international leader in the PET field and in the development of click chemistry and microfluidics integrated chemical reaction circuits (CRCs), as well as novel chemical-resistant polymers. The team will develop new CRCs that accelerate the discovery of high-affinity protein ligands through in situ click chemistry, as well as CRCs that allow the production of research quantities of radioactive [F-18]-containing PET probes targeting Akt. The specific aims are as follows: (1) Develop microfluidics CRCs for in situ click chemistry screening, including the interface with mass spectrometry instruments. (2) Develop high-affinity ligands for the oncogenic kinase Akt through in situ click chemistry using fragments that carry [F-19] as part of their design in order to facilitate later introduction of the PET radionuclide [F-18]. (3) Develop microfluidics CRCs for probe synthesis and produce [F-18]-labeled high-affinity kinase ligands.